Image forming apparatuses for forming images by depositing toner on recording mediums are conventionally known. An image forming apparatus estimates the amount of toner adhering to a recording medium (toner adhesion amount) based on density of images of an original document (original-document image density). This image forming apparatus preliminary stores correlation between the toner adhesion amount and the original-document image density, and estimates the toner adhesion amount for each dot based on the original-document image density of the dot.